1. Field of the Invention
This invention relates to the fabrication of ceramic tile and more particularly to a ceramic tile obtained with a stonework base and furnished with a glazed, metallized layer which is resistant to acid rain, absorbs a lesser amount of water than tile traditional tiles and weighs less than them as well.
2. Description of the Related Art Including Information disclosed under 37 C.F.R. .sctn.1.97-1.99.
There have traditionally been two types of tiles, those called Arabic tiles and the Roman ones, both of which are obtained from baked clay which form, when they overlap laterally and longitudinally, a grooved or fluted roofing in the direction of the slope, which directs rainwater towards the eaves.
Another type of covering for the roof consists of slate slabs. The slates also called clay schists are rocks which are easily subdivided into sheets or laminas according to the parallel planes between them called schistose planes.
The slate rocks come from the transformation by hardening and lamination of clays which, after having undergone great pressures during the intense movements of the earth's crust, have lost their plastic nature, their colour and texture, due to the high content of carbon and bituminous substances. As a result of their relative light weight and their resistance, they are used in the making of roofs.
Eventually, mosaic roofs have also been covered with bright colours, but such coverings have sought and obtained an ornamental, decorative effect within Modernist architecture in which the mosaic plays a major role. A practical effect was never sought beyond the decorative one and its implantation was always carried out in a traditional manner, that is, the placement with mortar or cement, as if it were pavement.
The Roman and Arabic tiles commonly used in the southern countries, have in their favour, their diffusion, their proven effectiveness and their easy placement. Their negative aspects are their heavy weight, about forty kilos per square meter, a high humidity absorption index (about 16%) and a limited resistance to frost which in the best of the cases does not exceed 25 cycles of freezing - defrosting continually. In addition, they absorb a great deal of heat,and their resistance to pressure is about 100 Deca-Newtons for a thickness of between 15 and 20 millimeters. And finally, they require roofs which do not have a great deal of inclination and their traditional aspect only suits very classic constructions.
The slate used in the slabs in the coldest, rainy areas and with greater incidences of snowfalls and a freezing - defrosting system, turns out to be expensive and laborious to obtain, calibrate and place. It should be homogenized in terms of thickness and therefore needs to be defoliated with meticulous care, then cut and finally drilled.
Leaving aside the fact that the surface area to be covered must be carefully prepared, for example, with a copper plate base and that the slabs have to be run through and then anchored afterward s with hooks, the slate has always been more expensive than the tile due to its unit cost and the laborious nature of its placement.
The s late has, on its behalf, a greater water-proofing ability than the tile, it admits inclinations almost to a vertical position and has a high resistance to freezing - defrosting effects, but as a disadvantage, it costs more. In addition, it is less resistant to wind and requires very specialised manpower from the initial process of its obtainment until the final placement.
The greatest virtue of me tile in relation with the slate slab lies in the fact that the former one is obtained from an industrial process, in which the clays, moulding type, baking temperatures, have all been selected and stabilised to finally produce a homogenous product in terms of its characteristics, dimensions and costs. Slate, to the contrary, depends on the deposit of the rocks, the pressure of the formation and the contents of its composition.
Attempts have been made to replace the slate tile with slabs obtained through an industrial process, using pressed layers of materials with resins, glues or cement as the binding matter. However, a product capable of successfully meeting the costs of the tile and the services of the slate slab has not yet been achieved.